The EU's foreign policy chief, Javier Solana, said there was "no other route" apart from diplomacy.

"The position of the European Union is clear," said Mr Solana according to the AP. "We want to find a diplomatic solution to this, in particular to clarify to the fullest the nature of their nuclear programme."

Mr Solana outlined for the ministers the results of a meeting on Saturday between Iran and diplomats from the United States, the United Kingdom, France, Germany, China, and Russia, where Tehran was encouraged to halt its uranium enrichment in return for a package of economic and political carrots.

With the US for the first time sending a high-ranking diplomat to the meeting, expectations were high that better relations between the two main antagonists would bear fruit. However, Iran maintained that its nuclear programme had only peaceful purposes.

American secretary of state Condoleeza Rice described Iran's negotiations following the meeting as "not serious."

Mr Solana on Tuesday however said he hoped to have "to have clear and simple answers" from Tehran within two weeks' time.

The six nations and the EU have given Iran a fortnight to reply to the latest offer. If the response is unsatisfactory, further sanctions could be considered.

"The offer that has been made to Iran on the one hand...and the sanctions on the other, if they refuse to engage and reply, is exactly the right approach," said Mr Miliband following the EU ministers' meeting.